02488nas a2200265   4500008004100000022001400041245020700055210006900262260007300331300001200404490000800416520142000424653002101844653003601865653002101901653001701922653002401939653002601963653002901989653001402018653001202032100002702044700001902071856013202090       2009                        eng d  a1387-181100aDependence of Si-29 NMR chemical shielding properties of precursor silicate species, Q(0) on its local structure at the pre-nucleation stages of zeolite synthesis - a DFT based computational correlation0 aDependence of Si29 NMR chemical shielding properties of precurso  aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcJUN  a105-1130 v1223 a<p>The exploration for new zeolite structures with tailored framework architectures for enhanced catalytic applications requires the knowledge about their nucleation and crystallization at molecular level. Nuclear magnetic resonance (NMR) is one of the most widely tried techniques to understand this. However, by NMR, it is difficult to accurately assign the molecular level precursor silicate structures at the pre-nucleation stages of zeolite synthesis. Hence, understanding the chemical shielding of such precursor molecules using quantum mechanical (QM) computations is extremely useful. Alkali is a fundamental component in the alkali based hydrothermal zeolite synthesis and its nature plays a major role. In the present report, we attempt to understand the differences in the local structure of the primary building block such as Si(OH)(4) (Q(0) silicate species) due to the associated alkali and their influence on NMR chemical shielding properties. Present work reports the calculation of Si-29 NMIR isotropic chemical shifts of T species with different cations such as Na, K and Ca using density functional theory (DFT). Results of natural bonding orbital (NBO) analysis, Perturbation theory energy analysis and electron density iso-surfaces were employed to obtain a deeper insight about their influence on the chemical shielding and on zeolite synthesis. (C) 2009 Elsevier Inc. All rights reserved.</p>10aAb initio method10aDensity Functional Theory (DFT)10aElectron density10aNBO analysis10aPerturbation theory10aQ(0) silicate species10aSi-29 NMR chemical shift10asynthesis10azeolite1 aSelvaraj, Kaliaperumal1 aKurian, Reshmi  uhttps://library.ncl.res.in/content/dependence-si-29-nmr-chemical-shielding-properties-precursor-silicate-species-q0-its-local-002620nas a2200253   4500008004100000245012300041210006900164260000800233300001200241490000700253520171000260653002501970653002101995653002802016653003202044653001802076653002002094100002702114700002002141700002402161700002802185700002402213856012902237       2019                        eng d00aExperimental and theoretical charge density, intermolecular interactions and electrostatic properties of metronidazole0 aExperimental and theoretical charge density intermolecular inter  cDEC  a942-9530 v753 a<p>Metronidazole is a radiosensitizer; it crystallizes in the monoclinic system with space group P2(1)/c. The crystal structure of metronidazole has been determined from high-resolution X-ray diffraction measurements at 90 K with a resolution of (sin 0/lambda) max = 1.12 angstrom(-1). To understand the charge-density distribution and the electrostatic properties of metronidazole, a multipole model refinement was carried out using the Hansen-Coppens multipole formalism. The topological analysis of the electron density of metronidazole was performed using Bader's quantum theory of atoms in molecules to determine the electron density and the Laplacian of the electron density at the bond critical point of the molecule. The experimental results have been compared with the corresponding periodic theoretical calculation performed at the B3LYP/6-31G** level using CRYSTAL09. The topological analysis reveals that the N-O and C-NO2 exhibit less electron density as well as negative Laplacian of electron density. The molecular packing of crystal is stabilized by weak and strong inter- and intramolecular hydrogen bonding and H center dot center dot center dot H interactions. The topological analysis of O-H center dot center dot center dot N, C-H center dot center dot center dot O and H center dot center dot center dot H intra- and intermolecular interactions was also carried out. The electrostatic potential of metronidazole, calculated from the experiment, predicts the possible electrophilic and nucleophilic sites of the molecule; notably, the hydroxyl and the nitro groups exhibit large electronegative regions. The results have been compared with the corresponding theoretical results.</p>
10aatomic valence index10aElectron density10aElectrostatic potential10aintermolecular interactions10ametronidazole10aradiosensitizer1 aKalaiarasi, Chinnasamy1 aGeorge, Christy1 aGonnade, Rajesh, G.1 aHathwar, Venkatesha, R.1 aPoomani, Kumaradhas  uhttps://library.ncl.res.in/content/experimental-and-theoretical-charge-density-intermolecular-interactions-and-electrostatic02366nas a2200277   4500008004100000022001400041245014300055210006900198260000800267300001100275490000900286520137600295653001801671653002101689653002801710653003201738653001401770100002701784700003001811700002001841700002001861700002401881700002801905700002401933856013101957       2020                        eng d  a0022-286000aInvestigation of bond topological and electrostatic properties of plumbagin molecule: an experimental and theoretical charge density study0 aInvestigation of bond topological and electrostatic properties o  cNOV  a1287140 v12203 a<p>Plumbagin is a naturally occurring derivative with several medicinal properties including antioxidants, antifungal, antimalarial, leprosy and antitumor properties; their structural and electrostatic properties are yet to be determined. The crystal structure of plumbagin has been solved; it shows that the compound crystallizes in P2(1)/c space group with two molecules in the asymmetric unit. The electron density distribution of both molecules have determined from multipole model refinement. Among all the C-O bonds of both molecules (I &amp; II), the OH group connected C-O bond and the methyl group connected C-C bond exhibits less electron density and the negative Laplacian of electron density as well. Further, the electrostatic potential (ESP) surface of two plumbagin molecules show some difference in their electronegative regions. The carbonyl O-atoms exhibit high electronegative ESP regions which are the key reactive locations of plumbagin when bind with the active site of target protein and in the ESP map, an aromatic pi-cloud also observed in one of the molecule. The electron density distribution of O-H center dot center dot center dot O intermolecular interactions between the molecules I and II, reveals that these interactions are found very stronger than the other interactions in the crystal. (C) 2020 Elsevier B.V. All rights reserved.</p>
10aDipole moment10aElectron density10aElectrostatic potential10aintermolecular interactions10aPlumbagin1 aKalaiarasi, Chinnasamy1 aSivanandam, Magudeeswaran1 aSuganya, Suresh1 aChristy, George1 aGonnade, Rajesh, G.1 aHathwar, Venkatesha, R.1 aKumaradhas, Poomani  uhttps://library.ncl.res.in/content/investigation-bond-topological-and-electrostatic-properties-plumbagin-molecule-experimental